package Demo01;


import java.util.LinkedList;
import java.util.Queue;

/**
 * 两个队列实现栈
 */
class MyStack {
    Queue<Integer> qu1;
    Queue<Integer> qu2;
    public int usedSize;
    public MyStack() {
        qu1 = new LinkedList<>();
        qu2 = new LinkedList<>();
    }
    //1.入栈
    public void push(int x) {
        if (!qu1.isEmpty()) {
            qu1.offer(x);
        }else if(!qu2.isEmpty()){
            qu2.offer(x);
        }else {
            qu1.offer(x);
        }
        usedSize++;
    }
    //2.出栈
    public int pop() {
        if (empty()){
            return -1;
        }
        if (!qu1.isEmpty()){
            int curSize = qu1.size();
            for(int i = 0; i < curSize-1; i++){
                qu2.offer(qu1.poll());
            }
            usedSize--;
            return qu1.poll();
        }else{
            int curSize = qu2.size();
            for(int i = 0; i < curSize-1; i++){
                qu1.offer(qu2.poll());
            }
            usedSize--;
            return qu2.poll();
        }
    }
    //3.获取栈顶元素
    public int top() {
        if (empty()){
            return -1;
        }
        if (!qu1.isEmpty()){
            int curSize = qu1.size();
            int ret = -1;
            for(int i = 0; i < curSize; i++){
                ret = qu1.poll();
                qu2.offer(ret);
            }
            return ret;
        }else{
            int curSize = qu2.size();
            int ret = -1;
            for(int i = 0; i < curSize; i++){
                ret = qu2.poll();
                qu1.offer(ret);
            }
            return ret;
        }
    }

    public boolean empty1() {
        return usedSize == 0;
    }
    public boolean empty() {
        return qu1.isEmpty() && qu2.isEmpty();
    }
};